The present disclosure is a catheter with a flexible tip and shape retention and a method to guide the catheter through small body passages such as coronary arteries including those at acute angles.
Catheters, known in the art, are slender and flexible tubes inserted into a body cavity or passage to distend or maintain an internal passageway. The catheter can withdraw or introduce fluids or Insert medical devices such as a cardiac stent. Often, small distal branched body passages need to be catheterized. Such catheterizations may require negotiating the catheter through multiple compound curves of varied angles, including acute angles, through these several branchings. In this instance, an acute angle arises when the body branchings require the catheter to make a turn of greater than ninety degrees.
There are catheters known in the art designed to reach specific types of body cavities or passages. For example, a cardiac catheter is a long, fine catheter designed for passage, usually through small peripheral blood vessels and into the chambers of the heart under radiological control. Such catheters are often guided with assistance from a guidewire. A guidewire is a thin, usually flexible, wire that can be inserted into selected body cavities or passages to act as a guide for subsequent insertion of a stiffer or bulkier device, such as a catheter, balloon catheter or stent catheter.
Other catheters and guidewires can include bending or flexing tip members or other attached mechanisms to guide a catheter through branching passages of a body. For example, U.S. Pat. No. 5,401,258 to Voda describes a cardiovascular catheter having a straight proximal end and a bent distal end. U.S. Pat. No. 5,885,259 to Berg describes a catheter having a straight portion followed distally by a primary curved portion. U.S. Pat. No. 6,106,488 to Fleming et al. describes a guidewire having sections of varying stiffness. U.S. Pat. No. 4,020,829 to Wilson et al. describes a guidewire that passes through the lumen of a catheter. The guidewire and catheter are used together to guide the catheter to a desired location in the body passage. The guidewire can provide reinforcement for the thin wall of the catheter. Without this reinforcement, some catheters alone might simply wrinkle or fold back on itself.
Although guidewires and catheters with flexible tips are known in the art, there is a need for a catheter that can be used to catheterize small distal branch passages and can negotiate compound curves of varied angles, including greater than ninety degrees (acute angles in relation to the proximal artery), through several branchings. For example, angle passages greater than ninety degrees occur in fifteen to twenty-five percent of patients requiring angioplasty. To perform an angioplasty (i.e., using a balloon to open a blocked artery) of the coronary arteries or other such blood vessel in the body, a guidewire must first be positioned across the blockage to guide the advancement of the balloon. There are some arteries that arise at a very acute angle from the main artery making it impossible using current technology to position the guidewire in that branch. Further, small catheters known in the art have problems with torque, whip, and windup. Torque is a function of a braid configuration, diameter of the catheter and the flexibility of the materials used. Small catheters have torque problems due to this smaller diameter. Whip is usually caused by windup during torquing of the catheter. As torque builds, the catheter ultimately rotates, causing the stored energy to be released (i.e., whipped) often in unexpected and undesired amounts. Also whip occurs if the materials used are too stiff, especially in a bend area such as the aortic arch.
Although attempts have been made to alter the degree of curvature of a catheter's distal tip, they often require the use of additional or complicated features. These features often require more device manipulation time, thus increasing procedure time, patient discomfort, and increasing the patient's and physician's radiation dosage. Further, more “mechanized” devices increase the likelihood of device malfunction. Therefore, there is a desire and a need to provide a simple catheter having a soft, flexible, pre-formed distal tip that when used in combination with commercially available guidewires of variable stiffness results In the ability to control the direction and angle of advancement of the catheter. Such a device would allow catheterization of body passages, including those that arise at acute angles.